Highlights:
- add new endpoint to query for intentions by exact match
- using this endpoint from the CLI instead of the dump+filter approach
- enforcing that OSS can only read/write intentions with a SourceNS or
DestinationNS field of "default".
- preexisting OSS intentions with now-invalid namespace fields will
delete those intentions on initial election or for wildcard namespaces
an attempt will be made to downgrade them to "default" unless one
exists.
- also allow the '-namespace' CLI arg on all of the intention subcommands
- update lots of docs
